Echo and singing suppressor system



July 3, 1928. 1,675,412

, W. H. T. HOLDEN ECHO AND SINGING SUPPRESSOR SYSTEM Filed June 1, 1926 enzmlor Ganerqtn' WETIoldem MTORNEY Pamel 3, 1 118.] 1,675,412

UN i-Ares PATENT OFFICE. r

WILLIAM n5. '1. HOLDEN, or BnooxmrN, NEW Yonx, AssieNon: 'romnnIcAN-rnnrnoNE AND TELEGRAPH comramr, A CORPORATION or ew 2031:

.nc'no AND siNeING snrrn isson sYs'rmn Application med inne i, 192a. sria No. 113,021.

My invention relates to means for supportion of each path is a radio channel, and n piessing echoes and singing incoinmunicaassociated with the wire paths are radio tion systems, and more particularly to echo transmitting and receiving means designed and singing suppressor arrangements which ford'u'plex operatioiion a single frequency.

are applicable to two-way systems having a At each end of the doublepath circuit are o0- part of each path formed by a radio channel. the usual hybrid coil 'and balancing net- Echo and singing 1 suppressor arrangework. The repeaters and the delay circuits, ments applicable to long wire telephone cirincluded in the system asshown, are old and cuits are now well understood in the art, well understood" in the art. I i

For a description and explanation ofsuch -When speech is transmitted from station 65 systems, reference may be had to an article V to station E, the voice currents in the entitled Echo suppressors for long teleupper wire path associated with station W phone circuits byA; B. Clark and R. cause the operation of relay 7 associated Mathes, Journal of the American Institute with the amplifier-detector apparatus 5 of Electrical Engineers, .June' 1925,' page through other relays 6. It is understood 70 618 et e H that this operation can occur only. in re- The object of my invention is tOnPl'OVidB" sponse' to voice currents. The operation of means which will (1) permit dupleitopera relay .7 places a short-circuit across the 7 tion of a radio channel (forming part ofa wires of the lower channel associated with two-way communication system) without the station W. I I

the necessity of perfect balance when a In the upper wire channel are signal insingle frequency is used for transmitting in putand side-band generating means 9,, which both directions, (2) permit the operationof may] be of any suitable type. I associate the wire circuits of the system, which cirwith themeans 9 a generator-'10 which procuits employ repeaters, without the necessity duees a pilot toneof a frequency outside the of perfect balance and with the elimination speech band. This generating means 10 is I of echoes in such circuits, and (3) accomconnected as indicated in the drawing, so plish (1) and (2) above without the liability that the pilot tone may be S P ed o the of being operated by noise or static intersystem at a point not afiected' y noise or 0 ference. static, Connected to the relays 6 and op- My stem has many featuresin common erable therewithin' res use to voice curwith she system described in the above rents is the relay 8. i order to prevent identified article and shown in Fig. 7 on. singing, the circuit between the signal input page 622 thereof.- In particular, I employ aiidgenerating apparatus, and the trans- 35 certain controlling means which, operate mittmg antenna is'normally short-circuited.

only when speech is applied to the system. Now, when the relay 8 operates in response i I will now describe in detail the essential to the voice currents from station W in the features of my invention in one desirable upper wire path, this short-circuit is re- V embodiment, it being understood. that refermoved, and the outputs of the elements 9- 40 ence may be had to the above identified arand 10 are supplied to the transmitting ticle for that part of the system which is antennafor simultaneous transmision over old in the art and dqes not call for detailed the radio channel. Considering the descrip consideration herein. I he following de-. tion so far-given, itwill be seen that means scription is to. be read with reference to the pr v d for Preventing echoes and sing 45 accompanying drawing. Figure 1 of the mg in the left. half of thesystem when drawing. shows diagrammatically and n speech 1s transmitted from station W, and, h part schematically the two-way communicain addition, means are provided for transtion system. embodying my invention, and mitting simultaneously with the voice sig- Fi 2 shows diagrammatically and in denals a distinctive pilot tone. 1

5o tai certain elements forming a part of the- In-ther1ght half of the system in the upp per channe there are provided a receiving The station W and the station E are inantenna and suitable radio receiving appa terconnectedxby a two-way telephone system ratus.- The speech from station W, accomhaving over a part of its length paths adaptpanied by the. pilot tone, passes over the 5 ed to transmit in opposite directions. A upper wire channel, and there is produced 11 the operation of the amplifier-detector 12 and the associated relay 13. This amplifier-detector apparatus is shown in greater detail in Fig. 2 of the drawing and will be further discussed below. It is tuned to operate only inresponse to the pilot tone from station W tostation E. Upon the operation of relay 13, a short-circuit is placed across the lower .pair of wires associated with station E, disabling that section of the transmission path from station E to station W.

When speech is transmitted from station E to station IV, the operation of the system .currents to the lower radio channel.

is similar to that described above. Through the amplifier-detector apparatus 5', voice currents operate relays 6 and 7', the opera- IV. Upon operation, the relay 13 places a short-circuit across the upper pair of wires associated with station this action corresponding to the action of the relay 13 in the case of transmission from station W to station \Ve thus have echoes and singing suppressed.

The sharpnessof tuning of the selective circuits associated with the apparatus 12 and 12' is so chosen that the energy of static contained in this band is relatively small, whereby there is an increase of the ratio of the signals controlling the echo and singing suppressor to the noise and static. This sharpness of tuning should not be increased to such an extent that the time required for the operation of the device is seriously increased, as such an increase might require the use of additional delay circuits.

For the structural details of the ampli-.

tier-detector circuits 5 and 5', reference may be had to the article identified above, and particularly to Fig. 3 on page 620.

Fig. 2 of the drawing shows in detail my arrangement of the elements 12 and 12, the letters X and Y serving to establish a clear connection between the showing of? Fig. 1

and that of Fig. 2. The vacuum tube 15 is the amplifier of this circuit, and the vacuum tube 16 is the detector. Batteries 17, 18 and 19 are the sources of filament current, plate voltage, and grid volta e, respectively. Included in this detail or the system are the tuned circuits 21 and 22. In the case of the amplifier-detector 12, these circuits are so tuned that the apparatus operates only in response tothe pilot tone from station W to station E. In the case of the apparatus 12' these circuits are so tuned that operation occurs only in response to the pilot tone from station E to station W. A relay 20 is'included in the plate circuit of the detector tube 16, and the operation of this relay causes the operation of relay 13 or relay '13, as the case may be, which relay functions to short-circuit the opposite line.

While the invention has been described in one specific embodiment which is deemed desirable and as applied toone type of twoway communication system,it is to be understood that this description is merely for the purpose of illustration and in no way limits the scope of the invention, which is defined in the appended claims.

I claim:

1. .In a two-way system for the transmission of speech, including combined wire andradio paths adapted to transmit in opposite directions, means associated with the outgoing wire section of one of said paths for generating a pilot tone, means operable by voice currents in said section for disabling the incoming wire section of the opposite path and for supplying said pilot tone to the first path for transmission simultaneously with the voice, and means operable substantially only in response to said pilot tone for dlsablin the distant outgoing wire section of sai opposite path.

2. In a two-way communication system in which, speech is transmitted between distant points by modulated alternating 'currents of frequencies above the voice range, said system including combined wire and radio paths adapted to transmit in opposite directions; echo and singing suppressor arrangements, including in association with the outgoing wire sectlon of one of 681d paths means for generating a ilot tone of a distinctive frequenc outsi e the voice ran e, means opera-b e by voice currents in sai section for disabling the incoming wire section of the opposite path and for supplying said pilot tone to the first path for transmission simultaneously with the voice, and means operable substantially only in response to said pilot tone for disabling the distant outgoing wire section of said opposite path. I

3. In a two way system for the transmis sion of speech, paths adapted to transmit in opposite directions, each of said paths comprising outgoing and incoming two-wire sections and an intervening radio channel; radio transmitting means associated with the outgoing wire section of each path; ra' dio receiving means associated with the in-' coming wire section of each path; means associated with said transmitting i'neans in I each path for generating a pilot tone; means associated with the out oing wire section of each path and 0 erable by voice currents therein for "disab ing the incoming section of the opposite path and for supplying said pilot toneto'the path carrying the voice currents for transmission simultaneously there- 'with; and means associated withthe incom-.

in wire section of each path and operable su stantially only in response to said pilottone for disabling the outgoing wire section of the opposite path.

' 4. In a two-way system for theftransmission of speech, wire paths adapted to transmit in' opposite directions, an interven-' ing radio channel and radio transmitting and receiving apparatus fonduplex opera tion thereovenon a singlefrequency, means associated with the outgoing'section of each wire path for generating a .pilot tone. of a distinctive frequency outside the voice range, means operable by voice currents in the outgoing section 'of each wire ath-for disabling the incoming section'of t e opposite wire path and for supplying said pilot tone to the path carrying t e voice currents for transmission over'the radio channel .si-

multaneously therewith, and means operable substantially only in response to said pilot tone for disabling the outgoing section of the o posite wire path.

5. n a two-way system for the transmission of speech, a first station, a second station, a four-wire circuit connected at each end thereof with one of said stationaand including a radio link, means associated with the first station for generating a pilot tone,

' means operable by voloe currents in the four wire circuit outgoing path connected with the first station for disabling the incoming path connected with said station and for supplying said pilot tone to said outgoin path for transmission over the radio li simultaneously with the voice, and means hame t'o this specification this 27th. day'of May, 1926.

WILLIAM H. T. HOLDEN.

In testimony whereof, I have signed my 

